From: damien (damien@xxxxxxxxxxx)
Date: Mon Sep 04 2000 - 13:44:26 GMT-3
Thanks for the replies, I am familiar with all the switching methods
and how they operate. What I would like to know is more on a practical
level. of what ratio speed links people have experienced problems with
out of sequence packets.
So if I have to equal cost routes to the same destination, either by
manipulating metrics or using variance or whatever, at what different
ratio's regarding the links speeds can you expect to see problems
using with fast-switching or process if any.
Variance will only switch per packet assuming you have process
switching enabled. Otherwise its per destination/ stream. So Variance
only accomodates route selection.......! forgot about that :~)
Therefore if I have 2 equal cost paths and use fast-switching/ cef
(without perpacket enabled)....there should be know issues with out of
sequence as the whole stream is switching via a single speed path ??
----- Original Message -----
From: Graham Shaw
To: 'damien' ; ccielab@groupstudy.com
Sent: Monday, September 04, 2000 1:09 PM
Subject: RE: Out of sequence packets
Variance is only used to inject unequal cost routes into the routing
table. As far as per packet of per destination. Depends if you are
process switching or interrupt context switching. (The path taken
depends on links.. If you have a route with a metric of 10000 and a
route with a metric of 20000 then 2 paths will go across the lower
route and 1 path will go across the upper route.)
Process switching will (on equal cost links) round robin packet. Fast
switching will switch packets based on per destination IP address.
Once the flow is built then it will always use the same outbound
interface until the cache is invalidated. Cef by defaults operates
exatly the same as fast switching (but a little faster).. However you
can have CEF do per packet load balancing on a per-interface basis if
required.
-----Original Message----
From: damien [mailto:damien@clara.co.uk]
Sent: 04 September 2000 15:10
To: ccielab@groupstudy.com
Subject: Out of sequence packets
Has anybody actually seen problems with out of sequence packets in
real life scenarios. The scenario I am interested in is the typical
example where there are switch paths to the same destination with one
link for example 2M and the other 1M? Does anybody have any proof of
concept testing done in a Lab were they can confirm at what different
speed ratios you are sure to experience problems based on certain
types of switching etc? I appreciate that there are a lot of
variables in this equation, e.g. type of switching, size of traffic
streams etc, etc. Any information/ experiences would be appreciated.
Can Variance overcome this issue ? Without reviewing my notes, I can
not remember whether Variance switches on stream or packet. If it is
stream. In theory, if a Router is performing stream switching, is it
fair to say that there should be no out of sequence issues due to the
fact that the entire stream is following a single path with fixed
speeds. If per packet switching is in use, they there maybe issues
with out of sequence packets due to the packets belonging to the same
stream being switched via different speed links.
I could go on an on........ :~)
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